Related papers: What are MACHOs? Interpreting LMC microlensing
There is now abundant evidence for the presence of large quantities of unseen matter surrounding normal galaxies, including our own$^{1,2}$. The nature of this `dark matter' is unknown, except that it cannot be made of normal stars, dust,…
We consider the contribution of neutron stars and black holes to the dynamical mass of galactic halos. In particular, we show that if these compact objects were produced by an early generation of stars with initial metallicity less than…
If the massive compact halo object (MACHO) fraction of the Galactic dark halo is f ~ 20% as suggested by some microlensing experiments, then about 1.2% of lensing events toward the Galactic bulge are due to MACHOs. For the 40% of these that…
All of the proposed explanations for the microlensing events observed towards the LMC have difficulties. One of these proposed explanations, LMC self-lensing, which invokes ordinary LMC stars as the long sought-after lenses, has recently…
The motivation for this paper is to review the limits set on the MACHO content of the Galactic halo by microlensing experiments in the direction of the Large Magellanic Cloud. This has been prompted by recent measurements of the Galactic…
Microlensing has established itself as a powerful new method for the detection of baryonic dark matter in the Galaxy. The theory of microlensing is sketched and its similarity with the optical effect of twinkling is explained. The bulk of…
The status of the microlensing search for galactic dark matter in the form of massive astronomical compact halo objects (machos) is reviewed. Unresolved issues are discussed, as well as possible ways to solve these.
We present an update of results from the search for microlensing towards the Large Magellanic Cloud (LMC) by EROS (Experience de Recherche d'Objets Sombres). We have now monitored 25 million stars over three years. Because of the small…
The nature and the location of the lenses discovered in the microlensing surveys done so far towards the LMC remain unclear. Motivated by these questions we computed the optical depth for the different intervening populations and the number…
The recent observations of microlensing events in the LMC by the MACHO and EROS collaborations suggest that an important fraction of the galactic halo is in the form of Massive Halo Objects (MHO) of about 0.1 M_{\odot}. Here, we argue that…
We present the basics of microlensing and give an overview of the results obtained so far. We also describe a scenario in which dark clusters of MACHOs (Massive Astrophysical Compact Halo Objects) and cold molecular clouds (mainly of $H_2$)…
Observations by the MACHO collaboration suggest that a significant proportion of the galactic halo dark matter is in the form of compact objects with typical masses $M\sim 0.5M_{\odot}$. One of the current mysteries is the nature and origin…
We discuss the implications of the more than 50 microlensing events seen by the EROS, MACHO, and OGLE collaborations for the composition of the halo of our galaxy. The event rates indicate that the halo mass fraction in MACHO's is less than…
We examine the chemical abundance constraints on a population of white dwarfs in the Halo of our Galaxy. We are motivated by microlensing evidence for massive compact halo objects (Machos) in the Galactic Halo, but our work constrains white…
The simplest interpretation of the microlensing events observed towards the Large Magellanic Clouds is that approximately half of the mass of the Milky Way halo is in the form of MAssive Compact Halo Objects with $M \sim 0.5 M_{\odot}$. It…
The possibility that Galactic halo MACHOs are white dwarfs has recently attracted much attention. Using the known properties of white dwarf binaries in the Galactic disk as a model, we estimate the possible contribution of halo white dwarf…
We report on our search for microlensing towards the Large Magellanic Cloud (LMC). Analysis of 5.7 years of photometry on 11.9 million stars in the LMC reveals 13 - 17 microlensing events. This is significantly more than the $\sim$ 2 to 4…
The observed microlensing events towards the LMC do not have yet a coherent explanation. If they are due to Galactic Halo objects, the nature of these objects is puzzling --- half the halo in dark 0.5 Msol objects. On the other hand,…
The observations of microlensing events in the Large Magellanic Cloud suggest that a sizable fraction (\sim 50%) of the galactic halo is in the form of MACHOs (Massive Astrophysical Compact Halo Objects) with an average mass $\sim 0.27…
Current microlensing searches calibrate the mass fraction of the Milky Way halo which is in the form of Massive Compact Halo Objects (MACHOs). We show that surveys like the Sloan Digital Sky Survey (SDSS) can probe the same quantity in…